sampling techniques

Question 1

random sampling

Answer 1

selecting a location using a random number generator. pros: non biased
cons: some parts of the river may be inaccessible

Question 2

stratified sampling

Answer 2

choosing sites based on what you are trying to find out

pros: accurate overview of river
cons: may be biased

Question 3

systematic sampling

Answer 3

choosing a site and taking intervals of a given value

pros: non biased
cons: some parts of the river may be inaccessible